1. Field of the Invention
The present invention relates to a mobile terminal provided with an information display screen which can display a route image showing a route from a starting location to a destination location specified by a user, a server which can transmit/receive data to/from the mobile terminal, and can produce a route according to the user's specification, a route guidance system which is provided with the mobile terminal and the server, programs which are used by the mobile terminal and the server, and a recording medium which records the programs.
The present invention more particularly relates to a mobile terminal such as a mobile phone and a PDA (Personal Digital Assistant) which can provide the user with a guidance route based on the user's current location and route data, a server which can transmit/receive data to/from the mobile terminal, a route guidance system which is provided with the mobile terminal and the server, programs which are used by the mobile terminal and the server, and a recording medium which records the programs.
2. Description of Prior Art
Recently, mobile terminals such as mobile phones have become more functional, as they are now equipped with navigation technology which guides/leads a user to a destination location by delivering to the mobile terminal a map image including a route to the destination location, showing the map image on the information display screen of the mobile terminal, and showing the current location on the map image by measuring the current location by means of the GPS (Global Positioning System). In Japanese Laid-Open Patent Publication No. 2003-214860 (paragraphs [0037], [0050] to [0055], FIGS. 4 to 6, 16, and 17, hereafter “Patent Document 1”), such navigation technology has been disclosed, in which a route is searched based on searching conditions such as a destination location transmitted from a mobile terminal, and data such as searching results is delivered to the mobile terminal to guide the user to the destination location.
In Patent Document 1, a server is made to search for an optimal route, treat the route as a road and assign it with a specific color, produce map data by building a route image (the road image with specified color) and incorporating it into a map image, and transmit the map data to the mobile terminal. Moreover, according to the technology described in Patent Document 1, the map image is constituted by multiple unit maps of a predetermined scale, whereas the route is built into the respective unit-maps, and data of the unit maps which includes the route, and the map image can be displayed on the screen of the mobile terminal based on the user's current location.
According to Patent Document 1, to determine a route, a user observes a map image, a route image, and an image of his-current location shown on the screen. For example, if the route is set to turn at an intersection, the user has to determine in which direction to turn, and may take a wrong direction. Moreover, when the user walks along a route while constantly looking at the screen of the mobile terminal, the user may hit other pedestrians or encounter other obstacles. Thus, because the user cannot always check the screen of the mobile terminal, he will likely miss an appropriate turn.
It is believed that the above problems can be solved by providing for a way of notifying the user when the location to make a turn has been reached or the direction in which to turn (such as “left” or “right”) by means of a voice or a displayed image, or a way of notifying the user of the distance to a location for making a turn.
However, according to the technology of prior art such as that described in Patent Document 1, the map data delivered from the server to the mobile terminal already incorporates the route data, and this is intended to reduce the amount of data to be transmitted and received. Accordingly, since the mobile terminal itself does not have the route data, the mobile terminal cannot determine the required notifying location (guide point), and is therefore incapable of providing such information.
In particular, when route data is built into multiple unit maps as described in Patent Document 1, if a location for making a turn exists on a unit map which has not been received, it is not possible to know such location for making a turn and the direction thereof until the unit map including such information is received. It is thus not possible to notify the user of the distance to such location for making a turn, or the direction of the turn to be made.
However, although a map need not be divided into unit maps, and entire map data incorporating a certain route may be transmitted to a mobile terminal which is capable of carrying out route searching, the mobile terminal must be equipped with a storage (memory) device with a large capacity for storing essential data such as map data and time tables of transportation facilities, which would entail additional cost in the production of the mobile terminal.
Further, when a mobile terminal processes route searching, load on the information processing device increases.